### Post by IBDaMann on May 29, 2019 16:16:55 GMT

**The Stefan-Boltzmann Law**

The Stefan-Boltzmann law calculates a black body's total thermal RADIANCE, measured in power per area, which is proportional to the body's (absolute) TEMPERATURE raised to the fourth power.

What is a "body"? It is any delimited, contiguous collection of matter. The Stefan-Boltzmann law apples to all matter, always, everywhere, whether it is an individual atom or a planet with an atmosphere and a hydrosphere.

What is a "black body"? Please refer to

**It is any body in which thermal activity is occurring. The modifier "black" simply implies a focus on the body's thermal properties, i.e. having associated thermal energy and thermally radiating that energy in the form of electromagnetic radiation. The Laws of Thermodynamics are hard-coded into the definition of a black body by establishing an equilibrium temperature T for each body absorbing thermal radiation from a constant source such that the body's temperature will rise until reaching T and then will achieve thermal equilibrium and will remain at temperature T.**

*Black Body Science (and Planck's Law)**:*

__The Stefan-Boltzmann Law__*Power / Area*=

*Temperature*

^{4}* S

*Boltzmann_Constant**

*Emissivity_Constant*

*Radiance*=

*Power*/

*Area*

**=**

*Radiance*

*Temperature*^{4}*

*****

*SBoltzmann_Constant*

*Emissivity_Constant***Radiance**: total

**power**of the

__combined emission of all wavelengths__of the body's thermal electromagnetic radiation per a given area.

**Power**: total

**power**of the

__combined emission of all wavelengths__of the body's thermal electromagnetic radiation.

**Area**: The surface area of emission.

**Temperature**: Absolute temperature, usually measured in Kelvins

**SBoltzmann_Constant**= 5.67 × 10^−8 watts / meter^2 squared per kelvin^4

**Emissivity_Constant**= A numerical coefficient strictly between 0.0 and 1.0 (0.0 and 1.0 are purely theoretical limits that do not exist in nature) representing the body's total thermal efficiency percentage to absorb and to emit thermal radiation over all combined wavelengths

**Additional Note**: The Stefan-Boltzmann law is derived by integrating Planck's law over all wavelengths. Whereas Planck's law yields a black body's thermal emission power for a particular wavelength at a given temperature, the Stefan-Boltzmann law yields the total aggregate thermal emission power for all wavelengths combined.